This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our main objective is to assess a method for the measurement of cardiac output and circualting blood volume during hemodialysis using the indicator dye dilution method. Knowledge of cardiac output and blood volume during the dialysis should help improve fluid management and prevent the occurrence of hypotensive episodes. An essential technical goal of the study is to show that circulating blood volume can be reliably estimated by non-invasive optical measurement of indocyanine green dye concentration in arterial blood circulating toward the hemodialyser following dye injection.